Add more nullability annotations

.github/workflows/main.yml

@@ -143,7 +143,6 @@ jobs:
           java-version: 11
       - name: 'Run CheckerFramework'
         uses: burrunan/gradle-cache-action@v1
-        name: Test
         with:
           job-id: checkerframework-jdk11
           arguments: --scan --no-parallel --no-daemon -PenableCheckerframework classes

build.gradle.kts

@@ -524,6 +524,11 @@ allprojects {
                 checkers.add("org.checkerframework.checker.nullness.NullnessChecker")
                 checkers.add("org.checkerframework.checker.optional.OptionalChecker")
                 checkers.add("org.checkerframework.checker.regex.RegexChecker")
+                extraJavacArgs.add("-Astubs=" +
+                        fileTree("$rootDir/src/main/config/checkerframework") {
+                            include("*.astub")
+                        }.asPath
+                )
             }
         }
 

linq4j/src/main/java/org/apache/calcite/linq4j/BaseQueryable.java

@@ -36,10 +36,10 @@ public abstract class BaseQueryable<TSource>
     extends AbstractQueryable<TSource> {
   protected final QueryProvider provider;
   protected final Type elementType;
-  protected final Expression expression;
+  protected final @Nullable Expression expression;
 
   public BaseQueryable(QueryProvider provider, Type elementType,
-      Expression expression) {
+      @Nullable Expression expression) {
     this.provider = provider;
     this.elementType = elementType;
     this.expression = expression;

linq4j/src/main/java/org/apache/calcite/linq4j/DefaultEnumerable.java

@@ -33,8 +33,8 @@
 import org.apache.calcite.linq4j.function.Predicate1;
 import org.apache.calcite.linq4j.function.Predicate2;
 
-import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.checker.nullness.qual.PolyNull;
 
 import java.math.BigDecimal;
 import java.util.Collection;
@@ -54,7 +54,7 @@
  *
  * @param <T> Element type
  */
-public abstract class DefaultEnumerable<T> implements OrderedEnumerable<T> {
+public abstract class DefaultEnumerable<T extends @Nullable Object> implements OrderedEnumerable<T> {
 
   /**
    * Derived classes might wish to override this method to return the "outer"
@@ -92,12 +92,12 @@ protected OrderedQueryable<T> asOrderedQueryable() {
     return EnumerableDefaults.asOrderedQueryable(this);
   }
 
-  public T aggregate(Function2<T, T, T> func) {
+  public @Nullable T aggregate(Function2<@Nullable T, T, T> func) {
     return EnumerableDefaults.aggregate(getThis(), func);
   }
 
-  public <TAccumulate> TAccumulate aggregate(TAccumulate seed,
-      Function2<TAccumulate, T, TAccumulate> func) {
+  public <TAccumulate> @PolyNull TAccumulate aggregate(@PolyNull TAccumulate seed,
+      Function2<@PolyNull TAccumulate, T, TAccumulate> func) {
     return EnumerableDefaults.aggregate(getThis(), seed, func);
   }
 
@@ -194,11 +194,11 @@ public <TKey> OrderedEnumerable<T> createOrderedEnumerable(
         keySelector, comparator, descending);
   }
 
-  public Enumerable<T> defaultIfEmpty() {
+  public Enumerable<@Nullable T> defaultIfEmpty() {
     return EnumerableDefaults.defaultIfEmpty(getThis());
   }
 
-  public Enumerable<T>  defaultIfEmpty(T value) {
+  public Enumerable<@PolyNull T> defaultIfEmpty(@PolyNull T value) {
     return EnumerableDefaults.defaultIfEmpty(getThis(), value);
   }
 
@@ -214,7 +214,7 @@ public T elementAt(int index) {
     return EnumerableDefaults.elementAt(getThis(), index);
   }
 
-  public T elementAtOrDefault(int index) {
+  public @Nullable T elementAtOrDefault(int index) {
     return EnumerableDefaults.elementAtOrDefault(getThis(), index);
   }
 
@@ -248,7 +248,7 @@ public T first(Predicate1<T> predicate) {
     return EnumerableDefaults.firstOrDefault(getThis());
   }
 
-  public T firstOrDefault(Predicate1<T> predicate) {
+  public @Nullable T firstOrDefault(Predicate1<T> predicate) {
     return EnumerableDefaults.firstOrDefault(getThis(), predicate);
   }
 
@@ -431,11 +431,11 @@ public T last(Predicate1<T> predicate) {
     return EnumerableDefaults.last(getThis(), predicate);
   }
 
-  public T lastOrDefault() {
+  public @Nullable T lastOrDefault() {
     return EnumerableDefaults.lastOrDefault(getThis());
   }
 
-  public T lastOrDefault(Predicate1<T> predicate) {
+  public @Nullable T lastOrDefault(Predicate1<T> predicate) {
     return EnumerableDefaults.lastOrDefault(getThis(), predicate);
   }
 
@@ -624,11 +624,11 @@ public T single(Predicate1<T> predicate) {
     return EnumerableDefaults.single(getThis(), predicate);
   }
 
-  public T singleOrDefault() {
+  public @Nullable T singleOrDefault() {
     return EnumerableDefaults.singleOrDefault(getThis());
   }
 
-  public T singleOrDefault(Predicate1<T> predicate) {
+  public @Nullable T singleOrDefault(Predicate1<T> predicate) {
     return EnumerableDefaults.singleOrDefault(getThis(), predicate);
   }
 

linq4j/src/main/java/org/apache/calcite/linq4j/DefaultQueryable.java

@@ -33,7 +33,7 @@
 import org.apache.calcite.linq4j.function.Predicate2;
 import org.apache.calcite.linq4j.tree.FunctionExpression;
 
-import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.math.BigDecimal;
 import java.util.Comparator;
@@ -150,7 +150,7 @@ public Enumerator<T> enumerator() {
     return factory.ofType(getThis(), clazz);
   }
 
-  @Override public Queryable<T> defaultIfEmpty() {
+  @Override public Queryable<@Nullable T> defaultIfEmpty() {
     return factory.defaultIfEmpty(getThis());
   }
 
@@ -164,7 +164,7 @@ public Enumerator<T> enumerator() {
 
   // End disambiguate
 
-  public T aggregate(FunctionExpression<Function2<T, T, T>> selector) {
+  public @Nullable T aggregate(FunctionExpression<Function2<@Nullable T, T, T>> selector) {
     return factory.aggregate(getThis(), selector);
   }
 
@@ -245,7 +245,7 @@ public T first(FunctionExpression<Predicate1<T>> predicate) {
     return factory.first(getThis(), predicate);
   }
 
-  public T firstOrDefault(FunctionExpression<Predicate1<T>> predicate) {
+  public @Nullable T firstOrDefault(FunctionExpression<Predicate1<T>> predicate) {
     return factory.firstOrDefault(getThis(), predicate);
   }
 
@@ -423,7 +423,7 @@ public T single(FunctionExpression<Predicate1<T>> predicate) {
     return factory.single(getThis(), predicate);
   }
 
-  public T singleOrDefault(FunctionExpression<Predicate1<T>> predicate) {
+  public @Nullable T singleOrDefault(FunctionExpression<Predicate1<T>> predicate) {
     return factory.singleOrDefault(getThis(), predicate);
   }